Abstract:
One of the widely spread causes of reservoir formation damage is fines migration. Migration of natural reservoir fines occur during commingled production of oil or gas with low-salinity water, during high-rate production or injection, with low-salinity waterflooding and its combinations with enhanced oil recovery. At least 10% of US$100 billion annual worldwide expenditure on prevention, mitigation and removal of formation damage is attributed to fines migration.The distinguishing features of natural reservoir fines migration are mobilization of the attached particles (for example, due to water salinity decrease and pH increase, water velocity increase), their capture by straining in the rock, permeability reduction and consequent decline in well productivity and injectivity. Detachment of fines from rock grain surfaces yields an insignificant increase in permeability, whereas particle straining in thin pore throats and consequent plugging of conducting paths causes significant permeability decline. The main sources of movable fine particles in natural reservoirs are kaolinite, chlorite and illite clays; quartz and silica particles can be mobilised in low-consolidated sandstones.Well productivity decline due to fines migration and formation damage during oil and gas production can be reliably predicted and effectively managed using laboratory data, mathematical modelling and field cases. The mathematical model for fines migration reliably predicts laboratory-based well behaviour. This model is mapped on the polymer option of Black-Oil model, allowing using commercial simulators for field development prediction under fines migration.Fines-migration management by production rate monitoring can prevent 3-4 times decline in well productivity index. Water blocking by deliberately induced fines migration and formation damage yields sweep increase during fines-assisted low salinity waterflooding with 8% of incremental recovery and 2-to-3,7 times reduction in produced water volumes; and significant water production decrease during pressure depletion of oil or gas fields with strong water support.These conclusions are supported by micro-scale physics theory, mathematical modelling, laboratory experiments, field data, 3D reservoir simulation and field test.
